spi: bitbang: Let spi_bitbang_start() take a reference to master

Many drivers that use bitbang library have a leak on probe error paths.
This is because once a spi_master_get() call succeeds, we need an additional
spi_master_put() call to free the memory.

Fix this issue by moving the code taking a reference to master to
spi_bitbang_start(), so spi_bitbang_start() will take a reference to master on
success. With this change, the caller is responsible for calling
spi_bitbang_stop() to decrement the reference and spi_master_put() as
counterpart of spi_alloc_master() to prevent a memory leak.

So now we have below patten for drivers using bitbang library:

probe:
spi_alloc_master        -> Init reference count to 1
spi_bitbang_start       -> Increment reference count
remove:
spi_bitbang_stop        -> Decrement reference count
spi_master_put          -> Decrement reference count (reference count reaches 0)

Fixup all users accordingly.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Suggested-by: Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>
Acked-by: Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>
Signed-off-by: Mark Brown <broonie@linaro.org>

1 files changed, 2 insertions, 3 deletions

diff --git a/drivers/spi/spi-gpio.c b/drivers/spi/spi-gpio.c
index 68b69fec13a9..14c01b44ca7a 100644
--- a/drivers/spi/spi-gpio.c
+++ b/drivers/spi/spi-gpio.c
@@ -467,7 +467,7 @@ static int spi_gpio_probe(struct platform_device *pdev)
         }
 #endif
 
-        spi_gpio->bitbang.master = spi_master_get(master);
+        spi_gpio->bitbang.master = master;
         spi_gpio->bitbang.chipselect = spi_gpio_chipselect;
 
         if ((master_flags & (SPI_MASTER_NO_TX | SPI_MASTER_NO_RX)) == 0) {
@@ -486,7 +486,6 @@ static int spi_gpio_probe(struct platform_device *pdev)
 
         status = spi_bitbang_start(&spi_gpio->bitbang);
         if (status < 0) {
-                spi_master_put(spi_gpio->bitbang.master);
 gpio_free:
                 if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
                         gpio_free(SPI_MISO_GPIO);
@@ -510,13 +509,13 @@ static int spi_gpio_remove(struct platform_device *pdev)
 
         /* stop() unregisters child devices too */
         status = spi_bitbang_stop(&spi_gpio->bitbang);
-        spi_master_put(spi_gpio->bitbang.master);
 
         if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
                 gpio_free(SPI_MISO_GPIO);
         if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
                 gpio_free(SPI_MOSI_GPIO);
         gpio_free(SPI_SCK_GPIO);
+        spi_master_put(spi_gpio->bitbang.master);
 
         return status;
 }